16663421 has 2 divisors, whose sum is σ = 16663422. Its totient is φ = 16663420.

The previous prime is 16663397. The next prime is 16663433. The reversal of 16663421 is 12436661.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10956100 + 5707321 = 3310^2 + 2389^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16663421 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16663441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8331710 + 8331711.

It is an arithmetic number, because the mean of its divisors is an integer number (8331711).

Almost surely, 2^16663421 is an apocalyptic number.

It is an amenable number.

16663421 is a deficient number, since it is larger than the sum of its proper divisors (1).

16663421 is an equidigital number, since it uses as much as digits as its factorization.

16663421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 29.

The square root of 16663421 is about 4082.0853739235. The cubic root of 16663421 is about 255.4198951549.

The spelling of 16663421 in words is "sixteen million, six hundred sixty-three thousand, four hundred twenty-one".